Network device and mobile station

ABSTRACT

A feedback packet is transmitted to an appropriate radio base station in ROHC control. A radio base station (eNB # 1 ) of the invention includes a transmission unit ( 12 ) configured to send a mobile station (UE) instruction information prohibiting “piggybacking (sending of a feedback packet while adding the feedback packet to a data packet)” in the ROHC control.

TECHNICAL FIELD

The present invention relates to a network device and a mobile station.

BACKGROUND ART

A packet with a small amount of data such as a voice packet has a largeamount of header data as compared to an amount of payload data, andresults in a waste of radio resources if the packet is transmitted orreceived without any change.

To address this, LTE (Long Term Evolution) is configured to subject sucha packet to header compression as shown in FIG. 5, and thus to avoid awaste of radio resources (see Non-patent documents 1 and 2, forexample).

This header compression is conducted by ROHC (RObust Header Compression)control in a PDCP (Packet Data Convergence Protocol) layer.

As shown in FIG. 6, in the ROCH control, “Compressor” on a sender sideis configured to perform the header compression by using contextinformation shared with “Decompressor” on a receiver side.

On the other hand, the “Decompressor” on the receiver side is configuredto decompress the header of the received packet by using the contextinformation shared with the “Compressor” on the sender side.

The “Decompressor” on the receiver side is configured to perform CRC(Cyclic Redundant Check) after decompressing the header of the receivedpacket, and thus to check whether or not the header of the receivedpacket is decompressed successfully.

If the header is not decompressed successfully, for example, a largeamount of packets are lost in a radio section and the “Decompressor” onthe receiver side and the “Compressor” on the sender side cause amismatch of the context information, the “Decompressor” on the receiverside notifies the “Compressor” on the sender side of the mismatch of thecontext information by transmitting a feedback packet thereto.

Here, when the “Compressor” on the sender side receives the feedbackpacket, the “Compressor” sends the “Decompressor” on the receiver sideinformation for matching the context information to be used.

Here, the “Decompressor” on the receiver side may transmit theabove-mentioned feedback packet alone, or send the feedback packet whileadding the feedback packet to a data packet (in other words, thefeedback packet may be “piggy-backed” on the data packet).

Meanwhile, in LTE Release-10, CA (Carrier Aggregation) to performcommunication by aggregating multiple CCs (Component Carriers) under thesame radio base station eNB, namely, “Intra-eNB CA” has been introducedin order to realize broadband communication over 20 MHz (for example,communication at 100 MHz) (see FIG. 7 (a)).

Thereafter, in LTE Release-12 and beyond, “Small Cell enhancement” hasbeen proposed and introduction of “Inter-eNB CA” to performcommunication by aggregating CCs (cells) under different radio basestations eNB is under study as one type of architecture more flexiblethan the conventional one.

For example, one possible operation by using the “Inter-eNB CA” is toperform communication of a C-plane signal that requires reliability witha cell #1 (macrocell) under a radio base station eNB #1 through an SRB(Signaling Radio Bearer), while to perform communication of a U-planesignal that requires broadband communication with a cell #11 (smallcell) under a radio base station eNB #11 through a DRB (Data RadioBearer) (see FIG. 7( b)).

In addition, a configuration in which a downlink packet and an uplinkpacket for a certain mobile station are transmitted and received fromand to different radio base stations eNB is under study as an operationform of the “Inter-eNB CA.”

Specifically, the configuration under study is that the radio basestation eNB #1 managing the cell #1 (macrocell) transmits the downlinkpacket to a mobile station UE and the mobile station UE transmits theuplink packet to the radio base station eNB #11 managing the cell #11(small cell), as shown in FIG. 8.

In the meantime, since a scheduler is mounted on each radio base stationeNB, a feedback packet (MAC/RLC-ACK/NACK) corresponding to the uplinkpacket has to be transmitted from the radio base station eNB #11 to themobile station UE and a feedback packet (MAC/RLC-ACK/NACK) correspondingto the downlink packet has to be transmitted from the mobile station UEto the radio base station eNB #1 as shown in FIG. 8.

PRIOR ART DOCUMENTS Non-Patent Documents

Non-patent document 1: 3GPP TS36.323

Non-patent document 2: RFC3095

Non-patent document 3: 3GPP TS36.300

SUMMARY OF THE INVENTION

However, when the operation form as shown in FIG. 8 is adopted, themobile station UE has to determine whether a packet to be transmitted isa data packet (Data-PDU: Protocol Data Unit) or a feedback packet(Control-PDU), and to identify the radio base station eNB of adestination of the packet.

In this regard, the mobile station UE can distinguish between a datapacket and a control packet (feedback packet) based on a prescribed bitfield in the packet (PDU).

However, whether or not to “piggy-back” the feedback packet on the datapacket in the ROHC control is an implementation matter of the mobilestation UE.

In this respect, there is a problem that if the feedback packet is“piggy-backed” on the data packet, the mobile station UE may not be ableto transmit the feedback packet to the appropriate radio base stationeNB.

This causes a problem that a mismatch of the context information occursbetween the “Compressor” of the radio base station eNB and the“Decompressor” of the mobile station UE.

The present invention has been made in view of the aforementionedproblems. An object of the present invention is to provide a networkdevice and a mobile station, which are capable of transmitting afeedback packet to an appropriate radio base station in ROHC control.

A first feature of the present invention is summarized as a networkdevice including: a transmission unit configured to transmit instructioninformation to a mobile station, the instruction information prohibitingsending of a feedback packet while adding the feedback packet to a datapacket in ROHC control.

A second feature of the present invention is summarized as a mobilestation including: a generation unit configured to generate a feedbackpacket in ROHC control. Here, the generation unit is configured todetermine whether or not to send a feedback packet while adding thefeedback packet to a data packet, based on instruction informationreceived from a network device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall configuration diagram of a mobile communicationsystem according to a first embodiment of the present invention.

FIG. 2 is a functional block diagram of a radio base station accordingto the first embodiment of the present invention.

FIG. 3 is a functional block diagram of a mobile station according tothe first embodiment of the present invention.

FIG. 4 is a flowchart showing an operation of the mobile stationaccording to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining a related art.

FIG. 6 is a diagram for explaining the related art.

FIG. 7 is a diagram for explaining the related art.

FIG. 8 is a diagram for explaining the related art.

DETAILED DESCRIPTION Mobile Communication System According to FirstEmbodiment of Present Invention

A mobile communication system according to a first embodiment of thepresent invention will be described with reference to FIG. 1 to FIG. 4.

As shown in FIG. 1, the mobile communication system according to thepresent embodiment includes a radio base station eNB #1 which manages acell #1, and a radio base station eNB #11 which manages a cell #11.

Here, the cell #11 is a small cell (phantom cell) and the cell #1 is amacrocell. Note that a coverage area of the cell #11 and a coverage areaof the cell #1 are deployed such that the coverage areas at leastpartially overlap each other.

The radio base station eNB #1 may also be referred to as a macro radiobase station (Macro-eNB), while the radio base station eNB #11 may alsobe referred to as a small radio base station (Small-eNB) or a phantomradio base station (Phantom-eNB).

Meanwhile, the mobile communication system according to the presentembodiment is an LTE-based mobile communication system. In the mobilecommunication system according to the present embodiment, a mobilestation UE is configured to be capable of performing the “Inter-eNB CA.”

Here, in the mobile communication system according to the presentembodiment, the mobile station UE is assumed to perform the “Inter-eNBCA” through the cell #1 under the radio base station eNB #1 and the cell#11 under the radio base station eNB #11.

Specifically, in the mobile communication system according to thepresent embodiment, the radio base station eNB #1 is configured totransmit a downlink packet to the mobile station UE and the mobilestation UE is configured to transmit an uplink packet to the radio basestation eNB #11.

Meanwhile, the mobile communication system according to the presentembodiment is configured such that a feedback packet (MAC/RLC-ACK/NACK)corresponding to the uplink packet is transmitted from the radio basestation eNB #11 to the mobile station UE and a feedback packet(MAC/RLC-ACK/NACK) corresponding to the downlink packet is transmittedfrom the mobile station UE to the radio base station eNB #1.

As shown in FIG. 2, the radio base station eNB #1 according to thepresent embodiment includes a management unit 11 and a transmission unit12.

The management unit 11 is configured to manage context information usedin ROHC control to be performed between the radio base station eNB #1and the mobile station UE.

Moreover, the management unit 11 is configured to manage informationconcerning the “Inter-eNB CA,” information concerning a bearer which isset between the radio base station eNB #1 and the mobile station UE, andthe like.

The transmission unit 12 is configured to transmit various signals tothe mobile station UE. For example, the transmission unit 12 isconfigured to send the mobile station UE instruction information whichprohibits “piggybacking” in the ROHC control.

Here, the instruction information may be designed to designate a radiobase station eNB or a cell to which a feedback packet is to betransmitted.

Meanwhile, the transmission unit 12 may be configured to transmit theabove-mentioned instruction information only when a radio base stationeNB which is a destination of the uplink packet transmitted from themobile station UE is different from a radio base station eNB which is asender of the downlink packet received by the mobile station UE.

Alternatively, the transmission unit 12 maybe configured to transmit theabove-mentioned instruction information only when a voice bearer for themobile station UE is set.

Here, the transmission unit 12 may be configured to transmit theinstruction information through a signal on an arbitrary layer such asan RRC layer, a PDCP layer, an RLC layer, an MAC layer, or a physicallayer.

Here, the functions shown in FIG. 2 may be provided to another networkdevice such as the radio base station eNB #11 or a mobile managementnode MME, instead of the radio base station eNB #1.

As shown in FIG. 3, the mobile station UE according to the presentembodiment includes a reception unit 21, a generation unit 22, and atransmission unit 23.

The reception unit 21 is configured to receive various signals from theradio base station eNB #1, the radio base station eNB #11, and the like.

For example, in the mobile communication system according to the presentembodiment, the reception unit 21 is configured to receive the downlinkpacket from the radio base station eNB #1 and to receive the feedbackpacket corresponding to the uplink packet from the radio base stationeNB #11.

Moreover, the reception unit 21 is configured to receive theabove-mentioned instruction information from the radio base station eNB#1. Here, the reception unit 21 may be configured to receive theabove-mentioned instruction information from the radio base station eNB#11, the mobile management node MME, or the like instead of the radiobase station eNB #1.

The generation unit 22 is configured to generate the uplink packet, thefeedback packet corresponding to the downlink packet, and the like to betransmitted therefrom.

Here, the generation unit 22 is configured to determine whether or notthe feedback packet should be “piggy-backed” on a data packet, based onthe instruction information received from the radio base station eNB #1or the like.

For example, if the above-mentioned instruction information prohibitsthe “piggybacking” in the ROHC control, then the generation unit 22 isconfigured to generate the feedback packet as an independent uplinkpacket (Control-PDU) without “piggy-backing” the feedback packet on thedata packet.

On the other hand, if the above-mentioned instruction information doesnot prohibit the “piggybacking” in the ROHC control, then the generationunit 22 is configured to “piggy-back” the feedback packet on the datapacket.

The transmission unit 23 is configured to transmit various signals tothe radio base station eNB #1, the radio base station eNB #11, and thelike.

For example, in the mobile communication system according to the presentembodiment, the transmission unit 23 is configured to send the radiobase station eNB #11 the uplink packet and to send the radio basestation eNB #1 the feedback packet corresponding to the downlink packet.

Here, the transmission unit 23 is configured to determine whether apacket to be transmitted is the data packet (Data-PDU) or the controlpacket (Control-PDU) based on a prescribed bit field in the packet, andthus to identify the radio base station eNB of a destination of thepacket.

An operation of the mobile communication system according to the presentembodiment, or more specifically, an operation of the mobile station UEaccording to the present embodiment will be described below withreference to FIG. 4.

As shown in FIG. 4, in step S1001, the mobile station UE generates thefeedback packet corresponding to the downlink packet. Then, in stepS1002, the mobile station UE determines whether or not the data packetto be transmitted is created.

In the case of “Yes, ” the operation proceeds to step S103. In the caseof “No,” the operation proceeds to step S105.

In step S103, based on the instruction information received from thenetwork device, the mobile station UE determines whether or not the“piggybacking” is prohibited in the ROHC control.

In the case of “No,” the operation proceeds to step S104. In the case of“Yes,” the operation proceeds to step S105.

In step S104, the mobile station UE “piggy-backs” the feedback packet onthe data packet, and transmits the packets to the radio base station eNB#11.

In step S105, the mobile station UE transmits the feedback packetindependently to the radio base station eNB #1 without “piggybacking”the feedback packet on the data packet.

The features of the present embodiment may also be expressed as follows.

A first feature of the present embodiment is summarized as a radio basestation eNB#1 (network device) including:

a transmission unit 12 configured to transmit instruction information toa mobile station UE, the instruction information prohibiting“piggybacking (sending of a feedback packet while adding the feedbackpacket to a data packet)” in ROHC control.

According to the above-described feature, by prohibiting the“piggybacking” in the ROHC control, it is possible to avoid a situationwhere it is likely that the mobile station UE cannot transmit thefeedback packet to an appropriate radio base station eNB due to“piggybacking” of the feedback packet on the data packet.

In the first feature of the present embodiment, the instructioninformation may be designed to designate any one of a radio base stationeNB and a cell to which the feedback packet is to be transmitted.

According to the above-described feature, it is possible to give a clearinstruction to the mobile station UE regarding the radio base stationeNB as the destination (a destination cell) of the above-mentionedfeedback packet.

In the first feature of the present embodiment, the transmission unit 12is configured to transmit the instruction information only when a radiobase station eNB being a destination of an uplink packet transmittedfrom the mobile station UE is different from a radio base station eNBbeing a sender of a downlink packet received by the mobile station UE.

According to the above-described feature, it is possible to assign amaximum value to an advantage of the effective use of radio resources bythe “piggybacking” by prohibiting the “piggybacking” in the ROHC controlonly when it is likely that the feedback packet cannot be transmitted tothe appropriate radio base station eNB.

In the first feature of the present embodiment, the transmission unit 12is configured to transmit the instruction information only when a voicebearer for the mobile station UE is set.

According to the above-described feature, it is possible to assign themaximum value to the advantage of the effective use of radio resourcesby the “piggyback” by prohibiting the “piggyback” in the ROHC controlonly when it is likely that the feedback packet cannot be transmitted tothe appropriate radio base station eNB.

A second feature of the present embodiment is summarized as a mobilestation UE including:

a generation unit 22 configured to generate a feedback packet in ROHCcontrol. Here, the generation unit 22 is configured to determine whetheror not to send the feedback packet while adding the feedback packet to adata packet, based on instruction information received from a radio basestation eNB#1 (network device).

According to the above-described features, since the mobile station UEdoes not “piggy-back” the feedback packet on the data packet in responseto the instruction from the network device, it is possible to avoid asituation where it is likely that the mobile station UE cannot transmitthe feedback packet to an appropriate radio base station eNB due to“piggybacking” of the feedback packet on the data packet.

In the second feature of the present embodiment, the instructioninformation is designed to designate any one of a radio base station eNBand a cell to which the feedback packet is to be transmitted.

According to the above-described feature, the mobile station UE canclearly grasp the radio base station eNB which is the destination (thedestination cell) of the above-mentioned feedback packet based on theinstruction information.

It should be noted that the foregoing operations of the mobile stationUE and the radio base stations eNB#1/eNB#11 may be implemented byhardware, may be implemented by a software module executed by aprocessor, or may be implemented in combination of the two.

The software module may be provided in a storage medium in any format,such as a RAM (Random Access Memory), a flash memory, a ROM (Read OnlyMemory), an EPROM (Erasable Programmable ROM), an EEPROM (ElectronicallyErasable and Programmable ROM), a register, a hard disk, a removabledisk, or a CD-ROM.

The storage medium is connected to a processor so that the processor canread and write information from and to the storage medium. Instead, thestorage medium may be integrated in a processor. The storage medium andthe processor may be provided inside an ASIC. Such an ASIC may beprovided in the mobile station UE and the radio base stationseNB#1/eNB#11. Otherwise, the storage medium and the processor may beprovided as discrete components inside the mobile station UE and theradio base stations eNB#1/eNB#11.

Hereinabove, the present invention has been described in detail by useof the foregoing embodiments. However, it is apparent to those skilledin the art that the present invention should not be limited to theembodiments described in the specification. The present invention can beimplemented as an altered or modified embodiment without departing fromthe spirit and scope of the present invention, which are determined bythe description of the scope of claims. Therefore, the description ofthe specification is intended for illustrative explanation only and doesnot impose any limited interpretation on the present invention.

Note that the entire content of Japanese Patent Application No.2013-053423 (filed on Mar. 15, 2013) is incorporated by reference in thepresent specification.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto provide a network device and a mobile station, which are capable oftransmitting a feedback packet to an appropriate radio base station inROHC control.

EXPLANATION OF THE REFERENCE NUMERALS

-   eNB #1, eNB #11 radio base station-   UE mobile station-   11 management unit-   12, 23 transmission unit-   21 reception unit-   22 generation unit

1. A network device comprising: a transmission unit configured to transmit instruction information to a mobile station, the instruction information prohibiting sending of a feedback packet while adding the feedback packet to a data packet in ROHC control.
 2. The network device according to claim 1, wherein the instruction information is designed to designate any one of a radio base station and a cell to which the feedback packet is to be transmitted.
 3. The network device according to claim 1, wherein the transmission unit is configured to transmit the instruction information only when a radio base station being a destination of an uplink packet transmitted from the mobile station is different from a radio base station being a sender of a downlink packet received by the mobile station.
 4. The network device according to claim 1, wherein the transmission unit is configured to transmit the instruction information only when a voice bearer for the mobile station is set.
 5. A mobile station comprising: a generation unit configured to generate a feedback packet in ROHC control, wherein the generation unit is configured to determine whether or not to send a feedback packet while adding the feedback packet to a data packet, based on instruction information received from a network device.
 6. The mobile station according to claim 5, wherein the instruction information is designed to designate any one of a radio base station and a cell to which the feedback packet is to be transmitted. 